First, the documentation is surprisingly helpful. I was walking through the Erlang document, and I was surprised at how quickly it refreshed my memory with the details of the language. You're not going to learn how to program from these guides, but if you already have skill in one language, they'll help you get some sort of basic proficiency with another.

Second, I love the simplicity behind the site. There's no clutter to be found, just a clean description of a dozen plus languages. You could easily over think the concept and try to make it some sort of ultimate portal to programming languages. But doing so, would probably mean that the concept would never get off the ground. The site creator did a great job of resisting the urge to make this complex.

Finally, I love the distributed nature of the site. The site owner doesn't depend on knowing all these languages perfectly. Instead, he's got a facility setup to take in submissions. That means that it can steadily grow.

This is the kind of site that a person can put together a rough version of over a weekend using existing tools. All that was needed was the idea and some mental effort to make it happen. It may be simple, but it's also quite powerful.